I'm scheduled for balloon sinuplasty on fri. my ent said he hasn't had anyone with adverse effects. what are/how likely are the risks during/post-op?

Lots of data: Balloon sinuplasty has been shown to be helpful for diseases of the frontal, sphenoid and maxillary sinuses; not so much for the ethmoid sinuses. The complications are similar to those of regular endoscopic sinus surgery but usually less severe due to the fact that there's no cutting technology used. Please ask your ENT for specifics on this. It really needs a personal conversation.

Low : When done for the right reasons for chronic sinusitis, sinus surgery (balloon or otherwise) is 90-95% effective at reducing symptoms. Recovery time is shorter (1-3 days) with balloon sinuplasty, and I do this procedure in-office with local anesthesia. Risks are low but similar to any sinus procedure: scarring, bleeding, infection, recurrent disease, eye/brain injury, need for further surgery, etc.